Archive for June, 2009

Think of a scientist – not anyone in particular, just a random individual working in the field. Got one? Did you picture a man or a woman? If it’s the former, you’re probably not alone. There have been a few times when I’ve only ever known a scientist through their surname on a citation and automatically assumed that they were a man, only to learn, to my chagrin, that they’re actually a woman. It’s always a galling reminder of how pervasive the stereotype of science as a male endeavour can be, even at an unconscious level.

Now, Brian Nosek from the University of Virgina, together with scientists from over 14 countries, has charted the extent of these implicit associations across the globe, and shown that they predict the size of the gender gap in school-level scientific achievement.

Nosek suggests that these biases and gender gaps feed off each other in a vicious cycle. The sex differences already present in the sciences, especially at the top echelons, are hard to miss and they can make stereotypes feel very real. In one study, women who saw a conference video where three in four attendees were men (a very real situation for many female scientists) felt less belonging and less desire to participate.

Stereotypes can also create themselves. Women who buy into stereotypes are less likely to take up a maths or science degree. Even if they refuse to be pigeonholed, they can be so stressed about conforming to a stereotype that they actually increase the odds of doing by taking a hit to their performance. This phenomenon is called “social identity threat” and it’s evident in research that shows women domore poorly in tests if they have previously been reminded of the supposed male superiority or even, simply, if their gender is highlighted.

Nosek’s group relied on a powerful tool that provides a standardised measure of the strength of stereotypes across different countries – the Implicit Association Test (IAT). The computer-based tests ask people to group words into pairs categories using assigned keys. One key might represent male words (he, boy) as well as science words (physics, chemistry), while the second key might represent female words or arts-related ones.

In martial arts classes, students are often taught to treat weapons as extensions of their own body. But this is more than just a metaphor. It turns out that when we use tools – not just swords and spears, but toothbrushes and rakes as well – our brain treats them as temporary body parts.

According to some psychologists, our brains rely on a mental representation of our bodies called the “body schema”, which allows us to coordinate our various parts and to interact with the world around us. Now, Lucilla Cardinali from INSERM, France has found that we incorporate tools into this mental plan after using them for just a few minutes. It’s confirmation of an idea that has been kicking around for almost a century.

She recruited 14 volunteers and asked them to grab a block in the middle of a table, that was always the same distance away. Then, they had to repeat the same actions with a grabber – a long, mechanical lever tipped with a two-fingered “hand” – and then a third time, with their own hand again.

Small LEDs on the volunteers’ hands allowed Cardinali to track their movements and calculate the speed and acceleration of their arms. She found that they reached for the block differently after they had been accustomed to the grabber, taking longer to accelerate their hands more slowly and to seize the block (although once they actually touched the blocks, they grasped them in just the same way as before). The delays even affected the speed at which they pointed at the block, a behaviour that wasn’t “trained” by the grabber.

There is a reason why there are no dinosaur geneticists – their careers would quickly become as extinct as the ‘terrible lizards’ themselves. Bones may fossilise, but soft tissues and molecules like DNA do not. Outside of the fictional world of Jurassic Park, dinosaurs have left no genetic traces for eager scientists to study.

Nonetheless, that is exactly what Chris Organ and Scott Edwards from Harvard University have managed to do. And it all started with a simple riddle: which came first, the chicken or the genome?

Like almost all birds, a chicken’s genome – its full complement of DNA – is remarkably small. DNA is made up of millions of units called ‘base pairs’, just like a book contains millions of letters. A typical bird genome is made up of about 1.5 billion of these base pairs, just half the number of the comparatively flabby human genome. Like their bodies, bird genomes are feather-weight and streamlined.

Some scientists have suggested that, over the course of evolution, birds shrunk their genetic packages to help them fly. Smaller genomes involve less DNA, which in turn can be housed in smaller cells. And smaller cells are more energy-efficient than larger ones, in the same way that a Mini is more efficient than a gas-guzzling SUV.

Talking with someone comes so naturally that we forget sometimes how skilful it is. Rhythms of conversation and cues of grammar need to be judged so that people can take their turns at talking without cutting off their partner or without leaving pregnant pauses. The former is rude, the latter awkward.

That’s certainly how things are usually conducted in English, but a new study suggests that this pattern of turn-taking applies across human cultures. By studying 10 languages from all over the world, Tanya Stivers from the Max Planck Institute for Psycholinguistics discovered a universally consistent pattern of avoiding overlaps and minimising pauses.

There are small variations certainly, but they are far smaller than stereotypes might suggest. Anecdotes and academic literature alike often claim that different cultures have radically different preferences for the tempo of conversations, from the reputed long pauses of Scandinavian speakers to the almost “simultaneous speech” of Jewish New Yorkers. But until now, no one had analysed these potential differences across a broad spectrum of languages and cultures.

Stivers did so by collecting video recordings of conversations in ten different languages from five continents – from English to Korean, and from Tzeltal (a Mayan language spoken in Mexico) to Yeli-Dyne (a language of just 4,000 speakers used in Papua New Guinea). In terms of grammar or sound, the tongues couldn’t be more different and their speakers vary from hunter-gatherers in Namibia to city-dwellers in Japan.

Social insects like ants, bees and wasps are some of the most successful animals on the planet. By acting as large super-organisms, they can achieve things that larger singular creatures cannot.

Their astounding selflessness is driven by an unusual way of handing down their genes, which means that females actually have more genes in common with their sisters than they do with their own daughters. And that makes them more likely to put the good of their colony sisters over their own reproductive legacy.

The more related the workers are to each other, the more willing they will be to co-operate. So you might expect colonies of social insects with fairly low genetic diversity to fare best. But that’s not the case, and Heather Matilla from Cornell University has found that exactly the opposite is true for bees.

Bee queens will often mate with several males (a strategy called polyandry). It’s an unexpected tactic, for it means that the queen’s daughters will be more genetically diverse and slightly less related to each other than they would be if they all shared the same father. And that could mean that selfless co-operation becomes less likely.

Despite this potential pitfall, social insect queens do frequently sleep with many males, and all species of honey bee do this. There must be some benefit, and Mattila has found it. Together with Thomas Seeley, she showed that a genetically diverse colony is actually a more productive and a stronger one.

Underwater, fish make very difficult prey. When they sense sudden disturbances in the water around them, they respond within five thousandths of a second with a defensive reflex called the C-start. Their body contorts into a C-shape and with a flick of the tail, they rapidly zoom away from the potential threat. But one predator has a way of turning the fish’s defence against it, persuading the fish to swim towards danger. It’s the tentacled snake.

The tentacled snake (Erpeton tentaculatum) is a bizarre species, easily recognised by the pair of short “tentacles” on the front of its head. The snake is a master fisherman and it hunts in the waterways of South-East Asia. It relies on ambush, anchoring its tail and twisted the front of its body into a distinctive J-shape. Thus contorted, it waits motionlessly for a fish to swim past. When it strikes, it does so explosively, covering the distance to its prey in 15-20 milliseconds.

So the battle between the tentacled snake and its prey is a contest between two extremely fast movements – the strike versus the C-start. But the snake has a way of tipping the odds in its favour – it feints. As the fish approaches, it ripples its body towards it, sending the hapless prey darting in the opposite direction, straight towards the snake’s angled head. The snake anticipates this and executes a predictive strike, aimed at the position where the fish will end up. Sometimes, the fish swim directly into the snake’s mouth.

For the fish, there is no turning back. Its C-start is driven by two giant nerve cells called Mauthner neurons. Disturbances in the water excite the nearest of this pair, which in turn excites a large network of motor neurons on one side of the fish’s body and blocks the equivalent network on the other side. That triggers the C-start and sends the fish in the opposite direction. This whole process takes mere milliseconds and once the direction is set, it can’t be reversed. The snake’s feint corrupts an otherwise adaptive behaviour, turning it from a defence into a death march.

In 1979, somewhere in Dartmoor, a butterfly died. That would hardly have been an exceptional event, but this individual was a Large Blue butterfly (Maculinea arion) and it was the last of its kind in the United Kingdom. Over more than a century, the Large Blue’s population had been declining and it was finally declared nationally extinct 30 years ago.

Now, it’s back. A bold conservation effort managed to work out the factors behind the butterfly’s decline, and resurrect this vanished species. The Large Blue’s reintroduction has been one of conservation’s flagship successes and it was the first time that efforts to save a declining butterfly had actually paid off.

The victory hinged on strong science. Rather than relying on speculation and optimistic measures, a team of scientists led by Jeremy Thomas, David Simcox and Ralph Clarke carefully analysed the factors behind the butterfly’s decline to find the best ways of reversing it. Work started in 1974 and the butterfly staged its comeback in 1983. Now, on the 25th anniversary of its reintroduction, Thomas, Simcoxand Clarke describe their efforts to bring the charismatic Large Blue back to England’s green and pleasant lands.

The Large Blue butterfly has a very strange lifestyle. When it hatches in July, its caterpillar feeds on thyme plants for three weeks and then drops to the ground to begin a more leisurely existence. The caterpillar so strongly mimics the smells and soundsof the ant Myrmica sabuleti that it is carried to the colony and cared for as if it were an actual ant. It spends the next 10 months of its life in this sheltered environment, and its mimicry ensures that its surrogate parents leave it alone, even when it eats their young.

Many living things, from chameleons to fish to squid, have the ability to change their colour. But flowers? Yes, over 450 species of flower have the ability to shapeshift, altering their colour and positions over the course of a day. The goal, as with many aspects of a flower’s nature, is communication. The secondary palette tells pollinators that a particular flower has already been visited and not only needs no pollen but has little nectar to offer as a reward. The visitor’s attentions (and the pollen it carries) are directed towards needier flowers.

The legume Desmodium setigerumis one of these colour-changers. Its small flowers, just a centimetre across, last for just a day and start off with a lilac hue. When pollinating bees land on the flower, their weight “trips” one of the petals and explosively reveals the flower’s reproductive parts.

After these visits, the flowers’ top petal falls down, obscuring the anthers and stamen, and the petals transform from lilac to white and turquoise. The whole process takes less than two hours. The move to turquoise happens naturally with age but visits from bees greatly speed up the process.

But this change works both ways. Pat Willmer from the University of St Andrews has found that D.setigenrum can reverse it transformation if it hasn’t received enough pollen from its visitor. Like shopkeepers flipping their “CLOSED” signs to “OPEN”, the flowers advertise themselves as back for business by once again shifting to a lilac colour. It gives them a second chance at being pollinated.

Discriminating against people who do not speak your language is a big problem. A new study suggests that the preferences that lead to these problems are hard-wired at a very young age. Even five-month-old infants, who can’t speak themselves, have preferences for native speakers and native accents.

The human talent for language is one of our crowning evolutionary achievements, allowing us to easily and accurately communicate with our fellows. But as the Biblical story of the Tower of Babel relates, linguistic differences can serve to drive us apart and act as massive barriers between different social groups.

These barriers can give rise to linguistic discrimination, a far more insidious problem that it seems at first. Language-based prejudices have led to horrific acts of human abuse, and even civil wars. Genocide often finds itself paired with linguicide, since a race can be killed off more thoroughly if their language follows them.

Even today, people in a linguistic minority can find themselves denied access to healthcare, or at a disadvantage when looking for jobs. The issue cuts to the heart of several ongoing debates, from the role of second languages in education to whether immigrants must become fluent in the tongue of their host country.

It should therefore be unsurprising to learn that we have strong preferences for our own language and for those who speak it. But Katherine Kinzler and colleagues from Harvard University, have found that we develop these preferences from an incredibly young age, before we can speak ourselves, and well before we can even hope to understand the social issues at stake.

In the time since the words “swine flu” first dominated the headlines, a group of scientists from three continents have been working to understand the origins of the new virus and to chart its evolutionary course. Today, they have published their timely results just as the World Health Organisation finally moved to phase six in its six-tier system, confirming what most of us already suspected – the world is facing the first global flu pandemic of the 21st century.

The team, led by Gavin Smith at the University of Hong Kong, compared over 800 viral genomes representing a broad spectrum of influenza A diversity. The viral menagerie included two samples of the current pandemic strain (the virus formerly known as swine flu and now referred to as swine-origin influenza virus (S-OIV)). Also in the mix were 15 newly sequenced swine strains from Hong Kong, 100 older swine strains, 411 from birds and 285 from humans.

The team used these genomes to build a viral family tree that shows the relationships between the strains and dates their origins. They found that S-OIV was borne of several viruses that circulate in pigs, with contributions from avian and human strains. The virus made the leap to humans several months before we twigged to its presence. It was spreading right under our noses, undetected because of our lack of surveillance of flu viruses in pigs.

This beautiful diagram (enlarge it) charts the origins of the current outbreak. Each set of eight lines and arrows represents the genome of the influenza virus, which consists of eight separate strands of RNA. The bold dots on the far right represent the strain that currently troubles us. Trace back the lines of its ancestry and you can see that every one of its eight genetic segments comes from a lineage of flu that had firmly established itself in pigs for at least a decade before the current outbreak. Go back further and you can see that some of the segments have their origins in human H3N2 subtypes and bird H1N1 subtypes in the 70s and 80s.